DR1-Y1MxN photocleavage generates DR1_a.

<p>(A) 150 nM DR1 empty was exposed to UV light for different periods of time (20 minutes, blue trace or 60 minutes purple trace) or not exposed to UV (0 minutes, black trace), finishing all exposures simultaneously. After UV exposure, samples were mixed with 25 nM labeled HA and binding to DR1 was measured by fluorescence polarization. The concentration of labeled HA bound to DR1 is plotted vs. time. (B) Same as in panel A, but using DR1 bound to unlabeled HA. (C) DR1-Y1MxN was exposed to UV light for different periods of time (5 minutes: red trace, 15 minutes: green trace, 20 minutes: blue trace, 30 minutes: orange trace, and 60 minutes: purple trace) or not exposed to UV (black trace), finishing all exposures simultaneously. Then, samples were mixed with 25 nM labeled HA and binding to DR1 was measured by fluorescence polarization. The concentration of labeled HA bound to DR1 is plotted vs. time. Panels A-C show the mean of one representative experiment performed with duplicate or triplicate samples out of three independent experiments. (D) Initial peptide binding rates were calculated as the slope of a linear fit to the initial time points of the peptide binding data shown in panel A, B and C. Black bars show the values for DR1 empty, DR1-HA or DR1-Y1MxN binding to labeled HA without being exposed to UV light (0 min.). In red, green, blue, orange and purple bars are shown the binding rates of DR1 empty, DR1-HA or DR1-Y1MxN to labeled HA after being exposed 5, 15, 20, 30 or 60 minutes to UV light respectively. Bars represent the mean and the error bars the standard deviation of the initial rates calculated from three independent experiments done with triplicate samples.